This proposal is based on the hypothesis that hydrogen peroxide (H2O2) is an important negative regulator of the in vitro proliferative response by stimulated human lymphocytes. Preliminary experiments indicate that addition of exogenous H2O2 depresses and addition of catalase, possibly by destroying endogenously produced H2O2, enhances proliferation of hyman lymphocytes. Future work will include assessment of the type of cell producing and responding to the H2O2, the timing of the action of H2O2, and the relation of the role of H2O2 to that of prostaglandin E2 (PGE2) as a modulator of proliferation. We confirm the requirement for monocytes in generation of suppressor T cells and hope to quantitate their helper effect versus their negative regulatory role via production of H2O2 and PGE2. Other experiments will utilize cells from patients with chronic granulomatous disease and their relatives to further define the relevance of monocyte H2O2 as a mediator of proliferation. Affected male patients have a defect in H2O2 production, their mothers have an intermediate level of production while their unaffected siblings have normal production. These cells will allow assessment of the consequence of decreased production of H2O2 free from possible artifacts induced when catalase is used to accelerate breakdown of this compound. Evidence from our laboratory and others indicates that monocytes from SLE patients are "activated", other data suggest that they produce excess PGE2. We will determine whether they also produce excess H2O2 and whether this second inhibitory compound accounts for the incomplete reversal of the inhibition of lymphocyte proliferation seen when SLE monocytes are treated with indomethacin to block PGE production. We will also explore the possibility that one consequence of inhibiting T cell proliferation by monocyte derived H2O2 may be to inhibit in vitro generation of suppressor T cells. This excessive production of H2O2 as well as PGE2 may account at least in part for the depressed in vitro suppressor T cell generation seen in patients with systemic lupus erythematosus.